The present invention relates to bridge and viaduct construction and pertains particularly to apparatus and methods for precast segmental span-by-span bridge construction.
The current technology used for rail and highway bridge construction includes span-by-span post tensioned precast concrete segmental construction. A typical bridge structure is defined cross-sectionally by a central load bearing span or web member and a pair of lateral wing or platform structures mounted to either side of the central load bearing body. The wings or lateral platform structures carry one or more lanes or tracks for vehicles on either side of the central body member. The bridge structure is supported between vertically extending piers positioned below the central body member.
A typical example of various bridge segments and a unique method for post-tensioning segmental bridge or viaduct structures are disclosed in U.S. Pat. No. 5,437,072 entitled RAPID TRANSIT VIADUCT WITH POST-TENSIONING CABLE SYSTEM, and of common assignment herewith. That patent is incorporated herein by reference as though fully set forth.
The techniques of construction of pre-cast concrete span-by-span bridges have been carried out in many ways. The different techniques normally employ various support structures normally involving girders and cranes and other equipment for supporting and handling the bridge segments. The precast segments can be supported during construction either from the top or from the bottom. When supported from the top, they hang under an overhead erection truss. When supported from the bottom, they rest on an underdeck erection truss.
One example of a girder support is illustrated in U.S. Pat. No. 5,386,782 entitled RAPID TRANSIT VIADUCT SYSTEM WITH CENTRAL PLATFORM STATION, of common assignment herewith, and incorporated herein by reference as though fully set forth. This system discloses the use of two parallel laterally spaced trusses used to support the segments under the wings, very close to the webs. The trusses rest on pier brackets secured to the top of the pier shaft and equipped with rollers to launch the trusses to the next pier.
Another erection or construction system is disclosed in U.S. Pat. No. 5,511,266, assigned to assignee hereof, which discloses a viaduct construction system wherein an erection girder spans and moves between viaduct piers for supporting structure and precast segments during assembly. This patent also discloses several examples of related prior art, and is incorporated herein by reference as though fully set forth.
The precast segments as previously pointed out can be supported during, construction either from the top or from the bottom. When supported from the top, they hang under an overhead erection truss which must be disassembled for movement from the piers of one span to the piers of the next span. When supported from the bottom, they rest on an underdeck erection truss which, if properly constructed and supported can be moved between piers without disassembly.
There is a need for an improved erection system and method which can easily move from span to span without disassembly for a substantially continuous assembly process.